Maturity effects on mineral concentration and uptake in Solanum nigrum L.

Abstract

The revitalisation of wild vegetables by consuming and cultivating them in home gardens is one of the strategies that agriculturalists have recently identified to combat food insecurity. However, data on mineral uptake with maturity are not available for a larger majority of wild vegetables. S. nigrum, one of the popular wild vegetables consumed in the Eastern Cape Province of South Africa, was cultivated both on the field and glasshouse to gain a better understanding of the uptake of some macrominerals as the plant matures. Five treatments (control; 100 kg N/ha; 8.13 t manure/ha; 100 kg N/ha + 8.13 t manure/ha and 50 kg N/ha + 4.07 t manure/ha) were set up in a Randomised Complete Block Design in both trials. The data were subjected to analysis of variance using MINITAB statistical software package. K (%) ranged between 3.11–6.98 in the glasshouse and 3.88–6.98 on the field; Ca (%) between 1.23–3.72 in the glasshouse and 1.39–3.98 on the field; Mg (%) between 0.31–0.93 in the glasshouse and 0.48–0.82 on the field; P (mg/kg) between 0.23–0.80 in the glasshouse and 0.29–0.77 on the field and Na (mg/kg) ranged between 749–3070 in the glasshouse and 187–3070 on the field. The application of 50 kg N/ha + 4.07 t manure/ha increased the uptake of a majority of the minerals. K, P and Na decreased with maturity while Ca increased and Mg varied. Although the current results indicate that for K, P and Na nutritional interventions, the leaves of S. nigrum are best harvested during the early phase of growth and the final phase for Ca, the concentration of these minerals has the potential to supply sufficient quantities of the minerals in human physiology at all stages of the plant's growth. This wild vegetable is therefore recommended for both consumption and cultivation.